There's a race of dog-headed people known as Cynocephaly (or Kynokephali) which literally means dog-head. Akephaloi is also used to describe the Blemmey who has no head. It would probably make sense to call horse-headed people Hippocephali or Ippokephaloi or something like that.
"Reverse-Centaur" would be very incorrect. "Centaur" or "Kentavros" is not a native Greek word, it's possibly imported from the Hindu Kinnara, (or some Persian or Assyrian iteration of the concept) which is either horse-head-like or centaur-like depending on when and where the term is used. In modern Southeast Asia, Kinnara is centaurine, but a bird body instead of a horse body, and this version seems to have eclipsed the earlier horse version.
I assume Ipotane as a race and Hippotes as "knight" sound similar like if you were comparing the English terms "horseman" and "horse man". So even though it's confusing, it's probably not incorrect.
If it helps to understand the headspace of the ancient proto-Greeks and Mycenaeans, they did not ride horses themselves, their horses pulled wagons and chariots. Their first exposure to horse riding would have been to someone like the Scythian raiders, and possibly misunderstood stories of Scythians from their neighboring empires, confusing "horsemen" as "horse men" and used the foreign word "centaur" to describe them. The myths of wild and violent centaurs might reflect these horse-riding raiders.